my personal experiences are:
2002 Kawi Ninja 250 x2 both ran flawlessly.
2002 Yamaha FZ1 came with a bad spark plug wire. It took me a few years to find out what was wrong with the bike because the bike only misfired once a while. I thought it was the nature of the bike
2007 Suzuki Burgman 400: the scoot ran great. It did have a noisy automatic clutch though. Known problem for the burgman.
2009 kawi KLR650: that bike burned a quart of oil every 1000 miles. I just had to sell it. checking the oil level after every ride was getting to me. Known problem for 2008 and 2009 model year. got better 2010 and on, so i hear.
Kawi 2011 ZX14: the motor is really smooth, almost no vibration at the handlebar at any rpm. smoothest bike i've ever ridden. It tends to run really hot in stop and go traffic, never over heat, but sooo close...
2013 s1krr: vibration around 4000rpm is worse than the thumper KLR. Then i hear, it is normal, and it did smooth out after i get pass 6000rpm. so no complains...
2012 Suzuki Vstrom 650: only have 50 miles on it, but so far i like it a lot. Good usable power for commuting. long travel suspension on the KLR and Vstrom is really good for back road riding in Jersey. Roads here are covered with potholes, with a sportbike, i have to carefully choose the path taken, with the KLR or the Vstrom, i just ride, take in the scenery, eating potholes like they don't even exist.